On Tue, Nov 29, 2011 at 5:40 PM, David Engel <david at istwok.net> wrote:
> I hadn't checked the code, but assumed the card
> number was only to open the right device file. No device file then no
> need for a card number.
Correct. The device number is used to distinguish multiple card when
opening the /dev/ceton/ctn91xx_mpeg<device>_<tuner> entry. When using
RTP, you just need to use the IP for access. In the deviceid, I just
use the string "RTP" in place of the device number to keep things
consistent.
> Ron, you've probably tested both device and
> RTP access quite a bit. Do you know of any reasons to prefer one over
> the other?
I've done plenty of testing with both, with RTP probably being used
more since my dev machine was using the Ceton in my production system
(though I did physically steal the card from my production system for
a couple of late night and overnight test runs). Clearly the RTP tuner
is more capable. Using RTP did seem to use slightly more CPU than the
file device, but now that I think of it, with the file device you
probably have the ceton driver doing much of the same thing behind the
scenes. This is one area that could perhaps use a little more testing.
One disadvantage of the file device I discovered is that it gets
locked out when something else is using the RTP interface. Normally
that's not such a big deal because as soon as the other client
finishes, the device becomes available again. However, in my testing,
where my production system is using 0.24 with the file device access,
and my remote dev system is using RTP, I found that if my dev system
didn't exit cleanly and shut down the RTP interface (by issuing the
RTSP "TEARDOWN" command), the Ceton was just as happy to keep
streaming forever. A few times I didn't notice this and thus my
production system got locked out and missed a few recordings. If you
use the RTP interface, you can always steal the RTP stream from the
other client just by issuing a new SETUP command to the RTSP
interface. For most users in most cases, this probably wouldn't be an
issue, but it is another advantage of RTP.
--
Ron Frazier